1. Field of the Invention
The present invention relates to the treatment of potable water to remove radioactive materials, and more particularly to the subterranean removal of such radioactive materials from water adjacent a well.
2. Description of the Related Art
Water for human consumption commonly is obtained for a well drilled deep into the earth. As water is pumped from the well, minerals and other substances are carried by the water from the well into the water distribution system. Several radioactive isotopes occur naturally in ground water. Among the isotopes of greatest concern are radium 226, radium 228, and several members of their decay series that emit alpha particles, referred to collectively as “gross alpha”. These radionuclides pose health threats and environmental problems in potable water supplied from the well.
In a municipal water system, the water drawn from a well frequently is processed above ground to remove undesirable substances, such as minerals which make the water “hard” inhibiting the cleaning action of soaps and detergents. Traditional methods of reducing radionuclide concentrations require substantial investments in treatment equipment and often create disposal problems for the process byproducts.
Attempts have been made at treating water while it still is in the aquifer. One of these involved injecting chemicals into the aquifer formation to filter out radionuclides as the water passed through the aquifer into the well. The chemicals either were injected as a slurry to deposit solids into the aquifer formation or were precipitated into the aquifer formation from a chemical reaction between two solutions. The common factor of these prior methods was the deposition of a solid that was foreign to the aquifer formation which solid then removed the radionuclides from the ground water around the well.
The prior in situ methods had to comply with governmental regulatory restrictions on injecting materials into aquifer formations which required that the wells be specially licensed. In addition, the process of depositing solids into the aquifer formation around a well has the undesirable effect of reducing the permeability of the formation. This may adversely affect the production capacity of the well or lead to undesirable precipitation reactions from chemical or biological processes which also can plug the formation over time.
Therefore, although subterranean treatment methods provided some improvement as compared to surface treatment processes, injection of foreign material into an aquifer formation to reduce radionuclides is generally considered undesirable and unnecessary.